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Guide to the Application of Genotyping to Tuberculosis Prevention and Control										Related Pages
										**Tuberculosis Genotyping Case Studies: How TB Programs Have Used Genotyping**
**Identification of Nontraditional Transmission Settings**
The Maryland Department of Health and Mental Hygiene described how universal genotyping can strengthen traditional TB control efforts. Maryland genotyped all of its *M. tuberculosis* isolates received during 1996 to 2000 and recently published the results (Cronin 2002).
Of 1,172 patients with genotyping results, genotypes from 436 matched those of at least one other patient in the state. Of the 436 clustered patients, 115 were thought to have acquired TB recently, and in 114 a setting of presumed transmission could be identified. Before the genotyping results were known, routine contact investigations identified epidemiologic links for 72 of the 114 patients (Table 2.3). During follow-up cluster investigations, additional information resulted in the identification of 42 patients with additional epidemiologic links.
Maryland’s cluster investigations, which were conducted after the genotyping results were available, helped to identify 30% more epidemiologic links than the original contact investigations. Many of these newly discovered epidemiologic links suggested that TB transmission occurred in settings that are often not asked about in routine contact investigations (e.g., homeless shelters, bars, churches, and nursing homes). The new information led TB program staff to screen previously unsuspected groups of persons.
**Table 2.3.** Transmission settings or relationships identified by either routine contact investigations or by cluster investigations for 114 patients with recently acquired tuberculosis — Maryland, 1996–2000.
Traditional
Transmission setting or relationship
Total patients with known setting
Setting identified by routine contact investigation (%)
Setting identified only by cluster investigation (%)Household
28
25 ( 89)
3 ( 11)Close relative
13
13 (100)
0Close friend
17
11 ( 65)
6 ( 35)Total traditional
58
49 ( 84)
9 ( 16)Nontraditional*
Transmission setting or relationship
Total patients with known setting
Setting identified by routine contact investigation (%)
Setting identified only by cluster investigation (%)Hospital
10
5 ( 50)
5 ( 50)Other workplace
6
6 (100)
0Social club
11
7 ( 64)
4 ( 36)Homeless shelter
5
0
5 (100)Bar
10
1 ( 10)
9 ( 90)Prison or jail
5
3 ( 60)
2 ( 40)Store
2
0
2 (100)Church
2
0
2 (100)Nursing home
2
0
2 (100)School
1
0
1 (100)Ship
1
1 (100)
0Mortuary
1
0
1 (100)Total nontraditional
56
23 ( 41)
33 ( 59)* The definition of nontraditional settings of transmission used by Maryland is not identical to the one used in Table 4.2.
							
					
						Page last reviewed:  September 1, 2012					Content source: 	Division of Tuberculosis Elimination, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention homeGuide to the Application of Genotyping to Tuberculosis Prevention and Control
Acknowledgments
Introduction to Tuberculosis Genotypingplus icon
Introduction to this Guide
Overview of Tuberculosis Genotyping
Overview of the CDC Tuberculosis Genotyping Program
TB Program Eligibility and Application Procedures
Tuberculosis Genotyping Case Studiesplus icon
Investigation of a Genotyping Cluster in a Low-Incidence State
Apparent Genotyping Cluster among Recent Immigrants from the Philippines
False-Positive Culture Investigation
Algorithm to Detect False-Positive Cultures
A Misdiagnosis that was Identified with Genotyping
Genotyping Used to Improve Contact and Cluster Investigations
Identification of Nontraditional Transmission Settings
Investigation of a Multistate Tuberculosis Outbreak
Homeless Shelter Outbreak Investigation
Using Genotyping to Evaluate the Impact of a Screening Program
CDC Tuberculosis Genotyping Laboratory Proceduresplus icon
Science behind Tuberculosis Genotyping
Description of Genotyping Methods
Submission of Isolates
Genotyping Results, Designation of Clusters, and Reporting
Suspected False-Positive Cultures
IS*6110*-based RFLP Analysis
Combining Genotyping and Epidemiologic Data to Improve Our Understanding of TB Transmissionplus icon
Definitions
Reading the Genotyping Laboratory Report
Comparing Genotyping and Epidemiologic Results from Two TB Patients
Comparing Genotyping and Epidemiologic Results from Three or More TB Patients
Clustering as a Surrogate Measure of Recent Transmission
Developing a Tuberculosis Genotyping Programplus icon
Developing a Written Plan
Initial Decisions
Establishing Procedures for:plus icon
Submitting Isolates
Receiving and Acting on Genotyping Results
Requesting RFLP Analysis
Submitting Additional Isolates from the Same Patient
Comparing Genotyping Results between Jurisdictions
False-Positive Cultures
Database Management and Quality Control
Special Issues
Applying Genotyping Results to Tuberculosis Control Practicesplus icon
Evaluating Matching Genotypes
Evaluating Nonmatching Genotypes
Suspected False-Positive Culture Investigations
Expanded Contact Investigations
Outbreak Investigations
Cluster Investigations
Monitoring Trends
Appendicesplus icon
Appendix A: Glossary and Abbreviations
Appendix B: References and Useful Resourcesplus icon
References Cited in the Guide
NTGSN Special Issue References
Information on Packaging and Shipping Infectious Substances
Core Steps of an Outbreak Investigation
Consultants Available to Offer Guidance To receive email updates about this page, enter your email address: Email Address			What's this?				Submit


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